Touch technologies are commonly used as input devices for a variety of electronic products. The usage of touch devices of various kinds is growing sharply due to the emergence of new mobile devices such as Personal Digital Assistants (PDA), tablet PCs, wireless flat panel displays (FPD), smart phones and other devices. Some of these devices are not connected to standard keyboards, mice or like input devices, which are deemed to limit their mobility. Instead there is a tendency to use touch input technologies of one kind or another.
One type of touch technology is a touch screen and/or transparent digitizer system overlaid on a display that can be operated by one or more fingers and/or styluses touching the screen. The finger or stylus can be used for selecting objects displayed on a screen, opening a document or scrolling within a window, entering data such as hand-written text and drawings, performing graphical operations such as moving or otherwise manipulating objects, or the like. Optionally a user is required to enter a security code with the finger or stylus to gain access to a computing device, a specific application and/or secure information stored in the device. The procedure of entering a security code is time consuming and at times cumbersome. Sometimes the security level of such systems is compromised when a user gains legitimate secured access and then leaves an authenticated session open.
U.S. Patent Application Publication No. 2010/0155153 entitled “Digitizer, Stylus and Method of Synchronization Therewith” which is hereby incorporated by reference in its entirety, describes a method for operating a digitizer with an autonomous asynchronous stylus. Typically the stylus is self-powered, e.g. battery operated that transmits signal bursts at a defined rate. It is described that the signal burst transmitted by the stylus can be modulated to encode identification data for identifying the stylus.
U.S. Patent Application Publication No. 2010/0079414 entitled “Apparatus, system, and methods for authentication on a publicly accessed shared interactive device” which is hereby incorporated by reference in its entirety, describes a digital surface that provides a display work area for each of a plurality of personal digital device (PDD) in communication with the digital surface. Each PDD establishes secured communication with the digital surface identified by a security token. Each PDD includes a stylus adapted to receive the security token for use in exchanges with the digital surface to thereby associate the exchange with the authenticated PDD with which it is coupled. Actions taken by a user of a stylus on the digital surface are authenticated based on the security token and based on the location of the stylus when the action is requested.
U.S. Patent Application Publication No. 2008/0141361 entitled “Systems and methods for lightweight authentication” which is hereby incorporated by reference in its entirety, describes techniques for the lightweight authentication of a user to an application, a computer or other device. An interaction element such as a stylus, a pen or a marker is uniquely identified with an authentication sensor embedded within a tablet personal computer. The interactive element is associated with a user and includes an identification element that is either passive or active. The proximity of the identification element to the authentication sensor during data entry operations to the authentication sensor, signals the controlled application that the user has been authenticated.
U.S. Pat. No. 7,843,439, entitled “Touch Detection for a Digitizer” assigned to N-trig Ltd., the contents of which is incorporated herein by reference, describes a detector for detecting both an electromagnetic stylus emitting a signal and interaction with finger touch. The detector typically includes a digitizer sensor with a grid of sensing conductive lines for sensing location of an electromagnetic stylus and a finger. The detector is capable of detecting simultaneous occurrences of multiple styluses and/or multiple finger touches.